Electric gas flow-pump

Abstract

The invention refers to an automotive electric gas flow-pump (10) with a rotor (20) comprising a rotor shaft (22), a pump wheel (24) and a motor rotor (32), wherein of the pump wheel (24) rotates in a pump wheel cavity (14), and a rolling bearing (40, 42) rotatably supporting the rotor shaft (22) at a static pump frame (16) and being in fluidic connection via a ring-interspace (44) with the pump wheel cavity (14), wherein a static air-permeable and dust-tight dust filter ring (50) is provided at the ring-interspace (44) thereby fluidically providing a dust-sealing between the pump wheel cavity (14) and the rolling bearing (40, 42). Since the dust-tight dust filter ring (50) is not radially pre-tensioned against the rotor shaft (22), the frictional forces between the filter ring (50) and the rotor shaft (22) are close to zero.

Description

[0001] DESCRIPTION

[0002] Electric gas flow-pump

[0003] The invention refers to an automotive electric gas flow-pump, more preferably to a so-called purge pump for pumping fuel vapor gas.

[0004] An electric fuel vapor gas pump is typically a high-speed flow-pump with a typical rotor speed of far above 10,000 rpm (rotations per minute). Typically, rolling bearings are used for supporting the rotor shaft, which rolling bearings are typically lubricated by a lubrication grease filling to guarantee a sufficient lifetime of the fuel vapor gas flow-pump. However, fuel vapor tends to wash out the grease filling, and dust particles can cause a substantial mechanical wear of the rolling bearings so that the rotor shaft needs to be sealed by a shaft sealing with respect to the pump wheel cavity. However, classical shaft sealings provide a substantial radial pressure against the rotating rotor shaft so that the shaft sealing body is continuously worn out and the frictional forces between the static shaft sealing body and the rotor shaft surface consume a considerable fraction of the rotational energy generated by the electric motor.

[0005] It is an object of the invention to provide a reliable automotive electric gas flow-pump having a high efficiency.

[0006] This object is solved with an automotive electric gas flow-pump with the features of main claim 1.

[0007] The automotive electric gas flow-pump according to the invention is provided with a rotor comprising a longitudinal rotor shaft, a pump wheel at one longitudinal end of the rotor shaft and a motor rotor preferably being provided at the other longitudinal rotor shaft end. The pump wheel rotates within a pump wheel cavity being defined by a pump housing.

[0008] The rotor shaft is rotatably supported by at least one rolling bearing, preferably by at least one ball bearing. The pump wheel cavity is in fluidic connection with the at least one rolling bearing via a ring-interspace surrounding the pump shaft. This ring-interspace is provided with a static air-permeable and dust-tight dust filter ring which thereby fluidically defines a dust sealing axially between the pump wheel cavity and the at least one rolling bearing so that the at least one rolling bearing is protected against the ingression of dust particles, liquid fuel drops and fuel vapor droplets from the pump wheel cavity.

[0009] The dust filter ring is not radially pretensioned against the rotating rotor shaft so that, after an initial running-in, no relevant wear and no relevant frictional forces arise. The dust filter ring does not need to be perfectly tight with respect to dust particles and fuel-vapor droplets but avoids a relevant transport of dust particles and fuel vapor droplets into the rolling bearing caused by convectional flow effects. Since the dust filter ring is not air-tight but permeable for air, no pressure differences can appear between both axial sides of the dust filter ring.

[0010] Preferably, at least one static motor coil and a motor drive electronics for electronically driving the at least one static motor coil is provided. The motor drive electronics includes a commutation electronics and comprises a set speed memory memorizing a set rotational motor speed of above 10,000 rpm. No mechanical commutator is provided. The automotive electric gas flow-pump is a fast-running pump which needs a sophisticated and easy-running rolling bearing which is sensitive for dust particles and for the rolling bearing lubricant being washed-out. Preferably, the rolling bearing is provided with a lifetime lubrication grease filling so that the rolling bearing is sufficiently protected against corrosion and is sufficiently lubricated for the lifetime of the automotive electric gas flow-pump.

[0011] Preferably, the dust filter ring is provided with a filter layer made of a felt body. The felt body can be any kind of a filter layer body suitable to withhold most of the dust particles and of the fuel vapor droplets. But the felt body is not necessarily physically completely tight for dust particles and fuel vapor droplets. Preferably, the felt body filter layer is sufficiently stiff so that no additional mechanical support for the dust filter ring is necessary to keep the dust filter ring in form over the lifetime of the automotive electric gas flow-pump.

[0012] Preferably, the dust filter is provided with a filter layer made of a fuel- liquid-tight membrane body which is a barrier for liquid fuel, fuel vapor droplets and for dust particles. The fuel-liquid-tight membrane body is transmissible for air so that a pressure equalizing air flow through the fuel-liquid-tight membrane is possible. Therefore, the same gas pressure is always present at both sides of the dust filter ring.

[0013] Preferably, the specific filter cut-off value of the filter layer is less than 100 pm, and preferably is less than 10 pm. Preferably, the filter ring is dust-tight for Arizona Dust A2 according to ISO 12103-1.

[0014] Preferably, the dust filter ring is provided with at least two different filter layers. More preferably, one filter layer is defined by a fuel-liquid-tight membrane body and the other filter layer is defined by a filter body providing sufficient mechanical support for the fuel-liquid-tight membrane body so that no additional support body is necessary for maintaining the dust filter ring in form for the lifetime of the automotive electric gas flowpump. Preferably, the fuel-liquid-tight filter layer is provided more proximal to the pump wheel than the other filter layer mechanically supporting the fuel-liquid-tight filter layer.

[0015] One embodiment of the invention is described with reference to the enclosed drawings, wherein figure 1 schematically shows a longitudinal cross-section of an automotive electric gas flow-pump according to the invention with a dust filter ring axially provided between the pump wheel cavity and one of the two rolling bearings, and figure 2 shows a longitudinal cross-section of the dust filter ring of figure 1 in more detail.

[0016] Figure 1 schematically shows a longitudinal cross-section of an automotive electric gas flow-pump 10 which is a so-called purge pump for pumping fuel vapor gas from a fuel tank or from a fuel vapor filter to a pumping target, for example to an air inlet tract of an automotive internal combustion engine (not shown).

[0017] The electric gas flow-pump 10 is provided with a rotor 20 comprising a metal rotor shaft 22, a plastic pump wheel 24 of the impeller-type, and a permanently magnetized motor rotor 32. The motor rotor 32 is provided at one axial end of the rotor shaft 22 and the pump wheel 24 is provided at the other axial end of the rotor shaft 22. The rotor 20 rotates around a longitudinal pump axis 20'. Two rolling bearings 40, 42 are provided at the shaft middle section. Both rolling bearings 40, 42 are therefore positioned axially between the pump wheel 24 and the motor rotor 32. The pump wheel 24 is provided with a distal inlet opening 25 and with a cylindrical outlet ring opening 26. A plastic pump housing 12 defines an axial pump inlet opening 18 being axially aligned with the pump wheel inlet opening 25 and defines a radial / tangential pump outlet opening 19. The pump housing 12 also defines a static pump frame 16 supporting the two rolling bearings 40, 42. The rolling bearings 40, 42 are both provided as ball bearings. Both rolling bearings 40, 42 are provided with a lifetime lubrication grease filling 80 which grease filling 80 avoids corrosion of the rolling bearings and lubricates the rolling bearings 40, 42.

[0018] The pump housing 12 defines a pump wheel cavity 14 housing the pump wheel 24. The pump housing 12 supports multiple static motor coils 34 being provided in the same transversal plane as the motor rotor 32. The pump housing 12 also houses a motor drive electronics 60 comprising several power semiconductors for driving the static motor coils 34 and comprising a commutation electronics driving the power semiconductors. The motor drive electronics 60 comprises a printed circuit board with a set speed memory 62 memorizing a set rotational motor speed S of above 10,000 rpm, for example of 60,000 rpm. The motor drive electronics 60 drives the motor coils 34 to generate a rotational rotor speed being the set motor speed S.

[0019] The pump housing 12 defines a ring-interspace 44 fluidically between the pump wheel cavity 14 and the closest rolling bearing 40. A static air permeable and dust-tight dust filter ring 50 is provided at the ringinterspace 44 and is arranged fluidically axially between the pump rotor cavity 14 and the closest rolling bearing 40.

[0020] The dust filter ring 50 is shown in more detail in figure 2: The dust filter ring 50 comprises two filter layers 52, 54 being held together by a clamping ring 58. The two filter layers 52, 54 can additionally be glued together. One filter layer 54 is made of a fuel-liquid-tight membrane body 54', whereas the other filter layer 52 is made of a felt body 52'.

[0021] The relatively thin fuel-liquid-tight membrane body 54' is made of PTFE and has a thickness of 0.1 to 0.3 mm. The fuel-liquid-tight membrane body 54' has a cut-off value F of less than 10 pm, for example 1,0 pm.

[0022] The much thicker filter layer felt body 52' is made of a soft hydrophobic material with a low specific friction with respect to the shaft surface 22' of the pump shaft 22 and being resistant and insensitive to water, fuel and oil. The filter layer felt body 52' typically has an axial thickness of 0,1 to 2,0 mm and mechanically supports the fuel-liquid-tight membrane body 54', the filter layer defined by felt body 52' is dust tight for Arizona Dust class A2 according to ISO 12103-1.

[0023] Both filter layers 52, 54 are filter rings, so that both filter layers 52, 54 have and define a circular filter layer opening 52", 54", both filter layer openings 52", 54" together defining a circular dust filter ring opening 56. The inner radial edges of the filter layer openings 52", 54" are only in a very slight frictional contact with the cylindrical outside shaft surface 22'. The dust filter ring 50 is not provided with any kind of a spring element generating radial forces for radially pushing the dust filter ring 50 against the pump shaft outer surface 22'.

Claims

CLAIMS1. An automotive electric gas flow-pump (10) with a rotor (20) comprising a rotor shaft (22), a pump wheel (24) and a motor rotor (32), wherein the pump wheel (24) rotates in a pump wheel cavity (14), and a rolling bearing (40, 42) rotatably supporting the rotor shaft (22) at a static pump frame (16) and being in fluidic connection via a ringinterspace (44) with the pump wheel cavity (14), wherein a static air-permeable and dust-tight dust filter ring (50) is provided at the ring-interspace (44) thereby fluidically providing a dustsealing between the pump wheel cavity (14) and the rolling bearing (40, 42).

2. The automotive electric gas flow-pump (10) of claim 1, comprising at least one static motor coil (34) and a motor drive electronics (60) for driving the at least one static motor coil (34), the motor drive electronics (60) including a set speed memory (62) memorizing a set rotational motor speed (S) of above 10,000 rpm.

3. The automotive electric gas flow-pump (10) of one of the preceding claims, wherein the rolling bearing (40, 42) is provided with a lubrication grease filling (80).

4. The automotive electric gas flow-pump (10) of one of the preceding claims, wherein the dust filter ring (50) is provided with a filter layer (52) made of a felt body (52').

5. The automotive electric gas flow-pump (10) of one of the preceding claims, wherein the dust filter ring (50) is provided with a filter layer (54) made of a fuel-liquid-tight membrane body (54').

6. The automotive electric gas flow-pump (10) of claim 5, wherein the specific filter cut-off value (F) of the filter layer (52, 54) is less than 100 pm, and is preferably less than 10 pm.

7. The automotive electric gas flow-pump (10) of one of the preceding claims, wherein the dust filter ring (50) is provided with at least two different filter layers (52, 54).

8. The automotive electric gas flow-pump (10) of claim 7 and 5 or 6, wherein the fuel-liquid-tight filter layer (54) is provided more proximal to the pump wheel (24) than the other filter layer (52).

Images